Graphic recorder with paper tensioning mechanism

ABSTRACT

Graphic recorder for use with strip chart having perforations on at least one edge and having first and second sprockets which are adapted to engage the perforations in the strip chart. The first and second sprockets are secured to first and second shafts. The first shaft is rotatably mounted in the framework in a fixed position, whereas the second shaft is rotatably mounted in the framework in such a manner so as to permit pivotal movement of the second shaft toward and away from the first shaft to permit tensioning of the strip chart. Means is provided for rotating the first and second shafts which accommodates the pivotal movement of the second shaft.

United States Patent Gordon GRAPHIC RECORDER WITH PAPER TENSIONING MECHANISM James Franklin Gordon, Saratoga, Calif. Zeta Research, Inc., Lafayette, Calif. Jan. 18, 1971 Int. Cl. ..G0ld 15/24, B65h 23/18 Field ofSearch ..346/1 36; 226/195; 242/753 References Cited UNITED STATES PATENTS 3,022,960 2/1962 Foster ..242/75.3 -l-lardway ..'....346/l36 Primary Examiner-Joseph W. Hartary Atrorney-Flehr, l-lohbach, Test, Albritton & Herbert [S 7] ABSTRACT Graphic recorder for use with strip chart having perforations on at least one edge and having first and second sprockets which are adapted to engage the perforations in the strip chart. The first and second sprockets are secured to first and second shafts. The first shaft is rotatably mounted in the framework in a fixed position, whereas the second shaft is rotatably mounted in the framework in such a manner so as to permit pivotal movement of the second shaft toward and away from the first shaft to permit tensioning of the strip chart. Means is provided for rotating the first and second shafts which accommodates the pivotal movement of the second shaft.

8 Claims, 6 Drawing Figures PATENTEDmzs I972 SHEET 1 BF 4 o 0 0 u 0 O 0 0 U vm v I I I I I I I l l I I I l I I I I l|+||l|||l|ll|l|lll| lllllll INVE'A ITOR. James E Gordon Attorneys INVENTOR.

u n w w m m fm 6 8 E A M4 m1 SHEET 3 [IF 4 PATENTEDMAR28 I972 GRAPHIC RECORDER WITH PAPER TENSIONING MECHANISM BACKGROUND OF THE INVENTION In the past, various mechanisms have been utilized to tension strip chart paper. However, such mechanisms have had disadvantages and, therefore, there is a need for a new and improved chart tensioning mechanism for use with graphic recorders.

SUMMARY OF THE INVENTION AND OBJECTS framework so as to permit pivotal movement of the second.

shaft toward and away from the first shaft whereby the strip chart can be tensioned. Means is provided for driving the first and second shafts while accommodating the pivotal movement of the second shaftand maintaining the angular registration of the sprockets.

In general, it is an object of the present invention to provide a graphic recorder which has a novel chart tensioning mechanism.

Another object of the invention is to provide a graphic recorder of the above character in which the sprockets can be affixed to the shafts.

Another object of the invention is to provide. a graphic recorder of the above character in which a substantially uniform and constant tension is applied by each sprocket to the chart paper.

Another object of the invention is to provide a graphic recorder of the above character in which the sprockets remain in angular agreement regardless of the positions of the sprockets.

Another object of the invention is to provide a graphic recorder of the above character in which the pivotally mounted shaft carries a pair of sprockets adapted to engage perforations on opposite sides of the strip chart and in which the means for pivotally mounting the. second shaft permits movement of one end of the second shaft with respect to the other.

Additional objects and features of the invention will appear from the following description in which the preferred embodiment is set forth in detail in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a top plan view of a graphic recorder incorporating the present invention with certain portions broken away.

FIG. 2 is a cross-sectional view taken along the line 2-2 of FIG. 1.

FIG. 3 is a cross-sectional viewtaken along the line 3-3 of FIG. 1.

FIG. 4 is a cross-sectional view taken along the line 4-4 of FIG. 3.

FIG. 5 is an enlarged top partial plan view of the graphic recorder with certain portions broken away.

FIG. 6 is a side elevational view. looking along the line 6-6 of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT The graphic recorder with paper tensioning mechanism is similar in many respects to the graphic recorder which is disclosed in copending application Ser. No. 868,339, filed Oct. 22, 1969. As disclosed therein, the graphic recorder consists of a framework 1 1 having spaced parallel front and rear plates 12 and 13 which are fastened together by plates 14 and 16 extending at rightangles thereto and secured thereto by suitable means such as screws (not shown). A pair of top plates 17 and 18 are mounted on the plates 12 and 13, and 14 and 16.

The top plate or lid 17 is L-shaped and is hingedly mounted on the framework 11 by securing the same to a rod 19 by suitable means such as screws 21. The rod 19 is pivotally mounted in the front and rear plates 12 and 13. The top cover plate 17 is movable between open and closed positions. It is retained in a closed position by a latch 22 which is pivotally mounted in the framework 11 and is yieldably urged into a lidengaging position by spring means (not shown) in the manner described in copending application Ser. No. 868,339, filed Oct. 22, 1969.

Side plates 26 and 27 and a bottom plate 30 are secured to the framework 11 to form a generally rectangular case 27. A top plate 28 is also secured to the framework 11 and serves to form a part of the case. The top plate 28 is provided with a planar portion 28a which provides a flat surface that serves as a platen or table.

Strip chart paper 31 of a conventional type such as fanfolded chart paper is provided with a plurality of perforations 32 along both edges of the paper and at least one edge of the same. The chart paper is adapted to travel over the top plate 28.

Means is provided for advancing the chart paper 31 over the top plate or platen 28 along the X-axis and consists of first and second shafts 34 and 36. A pair of sprockets 37 are mounted on the first shaft 34 in fixed spaced apart positions, and similarly a pair of sprockets 38 are mounted on the second shaft 36 in fixed spaced apart positions. The sprockets 37 and 38 are provided with teeth 39 spaced uniformly about the peripheries of the same which are adapted to engage the perforations 32 in the chart paper 31. As can be seen, the sprockets 37 and 38 are arranged in pairs with each pair being adapted to engage the perforations on one side. It should be appreciated that if desired it would be possible to eliminate one pair of the sprockets. Of each pair of sprockets, one can be considered to be a first sprocket and the other a second sprocket. The sprockets 37 and 38 are secured to the shafts 34 and 36 by suitable means such as set screws 41 so that the sprockets rotate with the shafts.

The first shaft 34 has its ends rotatably mounted in bearing assemblies 42 carried by the plates 14 and 16 and extends at right angles thereto. Means is provided for hingedly mounting or pivotally mounting the second shaft 36 so that it can be shiftedtoward and away from the first shaft 34 and also can have its opposite ends shift with respect to each other and with respect to the'corresponding ends of the first shaft 34. This means for permitting back and forth hinged motion or pivotal motion consists of arms 43 and 44 having ball bearing assemblies 46'mounted in one end of each of the same and which serve to rotatably mount the second shaft 36. As can be seen, the upper extremities of the arms 43 and 44 serve to carry the shaft 36. The lower end of the arm 43 is secured to a shaft 47 by suitable means such as a set screw 48 (FIG. 2). The shaft 47 is rotatably mounted in the side plates 14 and 16 by roller bearing assemblies (not shown). Two collars 51 are mounted on the other end of the shaft 47 so that they rotate with the shaft. A block 52 is mounted on the collars. The lower end of the arm 44 is secured to the block 52 by screws (not shown). From the foregoing description, it can be seen that the second shaft 36 is pivotally or hingedly mounted as hereinbefore described by the use of the arms 43 and 44 and that the sprocket wheels.38 carried thereby are free to rotate angu- Iarly.

Means is provided for driving the sprockets 37 and 38 so that they remain in substantial angular agreement during rotation of the same even though the position of the sprockets 38 relative to the sprockets 37 is changed. Such means consists of a plurality of nonslip driving elements in the form of pulleys 56 and 57. Pulley 56 is secured to the shaft 34 by suitable means such as set screw 58 and the pulley 57 is secured to the shaft 36 by set screw 59. The pulleys 56 and 57 are each provided with a pair of spaced parallel rows of teeth 61 arranged on the outer periphery of the pulleys. A flexible elongate nonstretchable element in the form of a belt 62 engages the pulleys 56 and 57. The belt 62 is of a conventional type such as one made of fiberglass with a neoprene covering on the same and having sideways extending teeth 63 which are adapted to cooperate or mate with the teeth 61 provided on the pulleys 56. and 57. The belt 62 is of an endless type and is reeved over the pulleys 56 and 57 and a toothed drive pulley 64 which is secured to a drive shaft66 by a set screw (not shown). The drive shaft 66 is rotatably mounted in the side wall 16 by a bearing assembly 67. The drive shaft 66 is connected by a coupling 68 to an output shaft 69 of a stepping motor 71 of a suitable type such as a Slo-syn driving motor supplied by the Superior Electric Company of Bristol, Conn. The stepping motor 71 is secured to the side plate 14 by screw 72.

Means is provided for guiding the belt 62 so that the amount of motion which may be encountered by the pivotal movement of the sprockets 38 will not cause angular disagreement between the sprockets 37 and 38 and consists of a pair of belt pulleys 73 and 74. The belt pulleys 73 and 74 are formed of a suitable material such as Teflon and are mounted upon ball bearing assemblies 76 which are secured to posts (not shown) carried by the wall 16 by screws 77. The belt pulleys 73 and 74 are positioned in such a manner that they are as close as practicably possible to the pivot point formed by the pivot shaft 47 for the arms 43 and 44. In order to eliminate all possible angular disagreement between the sprockets 37 and 38, it would be preferable that the pivot points for the rollers 73 and 74 be exactly coincident with the pivot point for the arms 43 and 44. However, it has been found that the arrangement which is shown in FIG. 2 of the drawings in which the pulleys 73 and 74 are as close as practicable to the pivot point for the pivot shaft 47 is satisfactory. The angular agreement between the sprockets 37 and 38 remains substantially unchanged as the arms 43 and 44 and the sprockets 38 carried thereby are pivoted angularly through a substantial angle. In other words, the shaft 36 and the sprockets 38 carried thereby can be considered to be a floating sprocket shaft which is free to move a limited amount in either direction. An idling or tightening roller 78 similar to the tightening rollers 73 and 74 is provided and is mounted upon an arm 79 which is held in a predetermined position by a screw 80 threaded into the side plate 18 to maintain the proper tension on the belt 62 as shown in FIG. 16.

For the tensioning of the chart paper, there must be means for tensioning at least two of the sprockets which, in this case, would be the two sprockets 38 carried by the floating shaft 36. In addition, one of the sprockets carried by the floating shaft must also be independently sprung from the other sprocket carried by the floating shaft for possible angular disagreements which can occur in the paper and because of the tolerances required in constructing the graphic recorder. Holes (not shown) are provided in the side walls and 16 to permit limited movement of the floating shaft 36. Thus, for both of the sprockets 38, there must be provided yieldable means for applying tension to the paper. A system utilizing a differential action is provided. It consists of a spring 81 which has one end secured to the upper end of the arm 43 by a screw 82 and has the other end secured to a pin 83 carried by the side wall 16. It can be seen that this spring 81 yieldably urges the floating shaft 36 in a direction towards the shaft 34. Means is provided for limiting the travel of the arm 43 in the clockwise direction or, in other words, the shaft 36 towards the shaft 34 and consists of a bar 80 which is secured to the side wall 16 by screws 85. A screw 84 is threaded into the bar 84 and has its inner end adapted to be engaged by the arm 43.

A lock nut 86 is provided on the screw 84 for locking the screw in the desired position.

Yieldable means is provided for urging the second shaft in the direction opposite which it is urged by the spring 81 and consists of a spring 87 which has one end secured to a post 88 which is threaded into a block 89 and locked in a predetermined position inthe block by a lock nut 91. The block 89 is secured to the shaft 47. The other end of the spring 87 is secured to a post 90'which is mounted in an L-shaped lever arm or dog 92 and is retained therein by nuts 93. The lever arm 92 is pivotally mounted upon a screw 96 which is threaded into the side plate 14. A spacer 97 is mounted on the screw and is held in place by a nut 98 on the screw. Washers 99 are provided on the screw 96 to properly position the lever arm 92. As shown particularly in FIG. 3, the lever arm 92 is adapted to be engaged by the top plate 17 when it is in the position shown in FIG. 3 and is adapted to be moved to the position shown in FIG. 6 in which the spring 87 is tensioned to move the arm 44 clockwise as viewed in FIG. 6 against the force of the spring 81.

The force exerted by the springs 81 and 87 is adjusted so that with the two working against each other, the floating shaft 36 is carried in an intermediate or median position. When the lid or top plate 17 is closed to shift the position of the lever arm 92, the tension on the spring 87 is increased with the result that the force on the floating shaft is in such a direction that the floating shaft moves away from the other shaft and thereby stretches the paper sheet 31.

Additional yieldable means is provided for permitting movement of one end of the floating shaft 36 without movement of the other end through a limited angle and consists of a U-shaped portion 890 formed integral with the block 89 in which the arm 44 extends between the legs of the U-shaped portion. Yieldable means is provided for yieldably urging the arm 44 in one direction within the U-shaped portion 89a and consists of a spring 101 which has one end secured to a threaded rod 102 threaded into the arm 44 and has the other end secured to a screw 103 threaded into the U-shaped portion 89a. Means is provided for limiting the amount of movement of the floating shaft 46 with respect to the shaft 47 and consists of an adjustment screw 106 which is threaded all the way through the arm 44 so that it extends through the arm and is adapted to engage an extension 89b of the U-shaped portion 890. An adjustment for the other direction is provided by screw 108 which is threaded into the portion 89a and is adapted to engage the other side of the arm 44 which is locked in the desired position by lock nut 109.

The remainder of the graphic recorder is very similar to that described in application Ser. No. 868,339, filed Oct. 22, 1969. A holddown frame 111 is provided for engaging the top plate or table 28 to hold down the chart paper31 so that the chart paper will remain in engagement with the sprockets 38. The holddown frame consists of a pair of side arm members 112 which are pivotally connected to the side-frame members 14 and 16 by screws 113 and 114. A spacer rod 116 extends between the side arm members 112 and is mounted therein. A shaft or rod 117 extends between the outer ends of the members 112 and has a sleeve 118 rotatably mounted thereon. The sleeve 118 carries rollers 119 on opposite ends which are provided with annular recesses 121 to accommodate the teeth of the sprockets 38. A plurality of additional disc-shaped rollers 122 are provided at spaced intervals on the sleeve 118.

Somewhat similar holddown means is provided which is associated with the sprockets 37 and is of a type described in copending application Ser. No. 868,339, filed Oct. 22, 1969.

A pen mechanism 126 similar to the pen mechanism described in application Ser. No. 868,339, filed Oct. 22, l969, is provided which is adapted to travel along the Y-axis for plotting on the chart paper. As described in said copending application, electronic means is provided for causing the desired movement of the pen mechanism 126. A cover 131 is provided on the top plate 17 and is generally L-shaped and covers the mechanism which is utilized for advancing and retracting the pen.

Operation of the graphic recorder incorporating the present invention may now be briefly described as follows. Let it be assumed that chart paper is to be loaded into the graphic recorder. When this is the case, the top' cover plate 17 is moved to an open position. The chart paper is then brought under the holddown frame 96 and over the top of the table 28 and the perforations 32 are brought into engagement with the sprockets 37 and 38. As soon as the perforations in the chart paper have been engaged by all four sprockets, the holddown frame can be shifted into a position to hold the chart paper in engagement with the sprockets 38. The top cover plate 17 can then be lowered towards its closed position so that the holddown assembly carried by the plate 17 engages the chart paper and retains it in engagement with the sprockets 37.

As the top cover plate 17 approaches its closed position, it engages the dog 92 and moves it downwardly to stretch the spring 87 to apply a force to the pivot shaft 47 which, in turn, causes a force to be applied to the arms 43 and 44 against the force of the spring 81 to move the floating shaft 36 away from the shaft 34 so that the chart paper is placed under tension as, for example, by a force of approximately 4 ounces by each sprocket. Since one end of the shaft 36 is capable of moving relative to the other because of the mounting provided for the arm 44, it is possible for the two sprockets 38 to accommodate slight differences in the chart paper so that both sides of the chart paper are placed under the same amount of tension.

After the chart paper has been loaded as hereinbefore described, the graphic recorder is ready for operation. The chart paper is under tension and can be advanced bidirectionally or in either direction.

In spite of all motions including the differential motion of the two floating sprockets 38, angular agreement is constantly maintained between the sprockets 36 and 38 even though the spacing between the sprockets changes. The adjustments provided by the screws 106 and 108 serve to limit the amount of shaft misalignment so that the misalignment stays within the tolerances which can be accommodated by the bearings.

When the lid or cover plate 117 is raised, it is desirable for the sprockets 38 to assume a position which is in agreement with the holes in the paper to facilitate removal and installation of the chart paper by the operator. The desired positioning of the sprockets 38 can be adjusted by the adjusting screws hereinbefore described.

It is apparent from the foregoing that there has been provided a graphic recorder which has novel means for permitting the chart paper to be tensioned during operation of the graphic recorder. The graphic recorder also is of a type which permits ready loading and unloading of the chart paper. Angular agreement is maintained between the sprockets even though the spacing between the sprockets may change. In addition, the tensioning provided by each sprocket remains substantially constant.

1 claim:

1. In a graphic recorder, a framework having a table adapted to carry a strip chart having perforations along at least one edge of the same, first and second shafts,a pair of sprockets, each of said sprockets having teeth adapted to engage the perforations in said strip chart, means for fixing one of said sprockets on each of said shafts so that the sprockets rotate with the shafts, means rotatably mounting said first shaft in said framework, means mounting said second shaft in said framework to permit rotational and pivotal movement of said second shaft toward and away from said first shaft, means for causing movement of said second shaft away from said first shaft to tension the strip chart, and means for driving said first and second shafts to rotate the same while accommodating the pivotal movement of said second shaft.

2. A graphic recorder as in claim 1 wherein said means to permit pivotal movement of said second shaft includes a pair of arms, means rotatably mounting said second shaft in said pair of arms, and means pivotally mounting said pair of arms on said framework.

3. A graphic recorder as in claim 2 wherein said means for driving said shafts includes first and second pulleys affixed to said first and second shafts respectively, a drive pulley, means for driving said drive pulley, a flexible elongate nonslip driving element engaging said drive pulley and said first and second pulleys, and means for (positioning said nonslip driving element so that it enters an leaves the pulley driving the second shaft at points which are in relatively close proximity to the axis of pivotal movement for said arms.

4. A graphic recorder as in claim 2 together with a shaft secured to one of said arms and pivotally mounting one of said arms, and means mounted on said additional shaft carrying saidsecond arm but permitting movement within a predetermined angle with respect to said additional shaft.

5. A graphic recorder as in claim 4 together with adjusting means for adjusting the range of movement of said second arm relative to the first arm.

6. A graphic recorder as in claim 1 wherein said means for causing pivotal movement of said second arm includes a lever arm, and means connecting said lever arm to said additional shaft, said framework including lever means for engaging said lever arm to move said lever arm into position to shift the position of said additional shaft.

7. In a graphic recorder, a framework having a table adapted to carry a strip chart having perforations along at least one edge of the same, first and second shafts, first and second sprockets, each of said sprockets having teeth adapted to engage the perforations in said teeth, means for fixing said first and second sprockets to said first and second shafts respectively so that the sprockets rotate with the shafts, means rotatably mounting one of said shafts in said framework, a pair of arms, means rotatably mounting said second shaft in said pair of arms, an additional shaft, one of said arms being fixed to said additional shaft, a lever arm mounted on said framework, yieldable means connecting said lever arm to said additional shaft, means for mounting said second arm on said additional shaft to permit pivotal movement of said arm, means for limiting the amount of pivotal movement of said second arm with respect to said additional shaft, cover means carried by said framework adapted to engage said lever arm to cause said second sprocket to be moved away from said first sprocket, and means for driving said first and second shafts in synchronism.

8. A graphic recorder as in claim 7 wherein said means for driving said first and second shafts in synchronism includes first and second pulleys secured to said first and second shafts, a drive pulley, a flexible elongate nonslip driving element engaging said drive pulley and said first and second pulleys, and means carried by the framework for causing the nonslip driving element to enter and leave the second drive pulley at points which are in relatively close proximity to the pivot axis for the additional shaft. 

1. In a graphic recorder, a framework having a table adapted to carry a strip chart having perforations along at least one edge of the same, first and second shafts, a pair of sprockets, each of said sprockets having teeth adapted to engage the perforations in said strip chart, means for fixing one of said sprockets on each of said shafts so that the sprockets rotate with the shafts, means rotatably mounting said first shaft in said framework, means mounting said second shaft in said framework to permit rotational and pivotal movement of said second shaft toward and away from said first shaft, means for causing movement of said second shaft away from said first shaft to tension the strip chart, and means for driving said first and second shafts to rotate the same while accommodating the pivotal movement of said second shaft.
 2. A graphic recorder as in claim 1 wherein said means to permit pivotal movement of said second shaft includes a pair of arms, means rotatably mounting said second shaft in said pair of arms, and means pivotally mounting said pair of arms on said framework.
 3. A graphic recorder as in claim 2 wherein said means for driving said shafts includes first and second pulleys affixed to said first and second shafts respectively, a drive pulley, means for driving said drive pulley, a flexible elongate non-slip driving element engaging said drive pulley and said first and second pulleys, and means for positioning said non-slip driving element so that it enters and leaves the pulley driving the second shaft at points which are in relatively close proximity to the axis of pivotal movement for said arms.
 4. A graphic recorder as in claim 2 together with a shaft secured to one of said arms and pivotally mounting one of said arms, and means mounted on said additional shaft carrying said second arm but permitting movement within a predetermined angle with respect to said additional shaft.
 5. A graphic recorder as in claim 4 together with adjusting means for adjusting the range of movement of said second arm relative to the first arm.
 6. A graphic recorder as in claim 1 wherein said means for causing pivotal movement of said second arm includes a lever arm, and means connecting said lever arm to said additional shaft, said framework including lever means for engaging said lever arm to move said lever arm into position to shift the position of said additional shaft.
 7. In a graphic recorder, a framework having a table adapted to carry a strip chart having perforations along at least one edge of the same, first and second shafts, first and second sprockets, each of said sprockets having teeth adapted to engage the perforations in said teeth, means for fixing said first and second sprockets to said first and second shafts respectively so that the sprockets rotate with the shafts, means rotatably mounting one of said shafts in said framework, a pair of arms, means rotatably mounting said second shaft in said pair of arms, an additional shaft, one of said arms being fixed to said additional shaft, a lever arm mounted on said framework, yieldable means connecting said lever arm to said additional shaft, means for mounting said second arm on said additional shaft to permit pivotal movement of said arm, means for limiting the amount of pivotal movement of said second arm with respect to said additional shaft, cover means carried by said framework adapted to engage said lever arm to cause said second sprocket to be moved away from said first sprocket, and means for driving said first and second shafts in synchronism.
 8. A graphic recorder as in claim 7 wherein said means for driving said first and second shafts in synchronism includes first and second pulleys secured to said first and second shafts, a drive pulley, a flexible elongate non-slip driving element engaging said drive pulley and said first and second pulleys, and means carried by the framework for causing the non-slip driving element to enter and leave the second drive pulley at points which are in relatively close proximity to the pivot axis for the additional shaft. 